Dental hand piece



Nov. 14, 1950 M. sTAUNT 2,529,824

DENTAL HAND PIECE Filed March 13, 1947 Patented Nov. 14, 1950 UNITED STATES PATENT DFFICE DENTAL HAND PIECE Martin Staunt, Chicago, Ill.

Application March 13, 1947, Serial No. 734,383

Z Claims.

The present invention relates to dental hand pieces, and is particularly concerned With dental hand pieces oi the type which are to be driven by means of a belt and pulley, and which includes a suitable chuck for holding the various drills, burrs, sanding wheels, etc. used with dental hand pieces.

The present application is a continuation-inpart of my prior application, Ser. No. 616,130, led September 13, 1945, entitled Dental Hand Pieces, Patent No. 2,445,891, issued July 27, 1948.

One oi the objects oi the invention is the provision oan improved dental hand piece ofthe class described having an improved form of pulley construction which is adapted to permit constant and effective lubrication, to protect the patient and the operator from the pulleys and belts and to operate for a long period ofA time Without necessity for repair or replacement.

Another object oi the invention is the provision of an improved hand piece construction particularly adapted to eliminate the trouble Which might be encountered Where the collet is engaged by an actuating member, and Where in the devices of theprior art the collet may tend to spread the actuating member until it tends to stick in its boreinstead of sliding freely and releasing the collet readily when the actu-ating rod is withdrawn.

Another object of the invention is the provision of an improved dental hand piece in which provision is made for driving `the hand piece at a plurality of different speeds so that, although the usual speed is available, the hand piece may also be driven at a higher speed for use with diamond cutting instruments. These diamond cutting instruments require a higher speed; but

' they cut more quickly and more coolly, thus reducing the heat in the mouth of the patient and reducing the tendency toward pain.

Another object of the invention is the provision of an improved hand piece particularly adapted to be used for driving diamond cutting instruments at a higher speed than the devices of the prior -art so that they may cut more quicklyl and more coolly, reducing the time of operation, reducing the heat, and alleviating the discomfort or pain borne by the patient.

Another object of the invention is the provision of an improved dental hand piece which is adapted to be manufactured at a 10W cost, which is sturdy, which grips the shank of a tool readily and releases it readi-li which may be operated at low or high speeds, and which may be used for a sil) long period of time without necessity for repair or replacement of its parts.'

Other objects and advantages of the invention will be app-arent from the following description and the accompanying drawings, in which similar characters of reference indicate similar parts throughout the several views.

Referring to the single sheet of drawings,

Fig-1 is a side elevational viewof a dental hand piece embodying my invention;

, Fig. 2 is a .fragmentary axial sectional view of the operating end of the hand piece; f

Fig. 3 is another fragmentary axial sectional view of the rear end portion of the hand piece;

Fig. 4 is a fragmentary sectional view, taken on a plane passing through the axis of the pulleys, that is the plane along the line fi-Q of Fig.- l.

The dental hand piece embodying my invention is shown in side elevation in Fig. l, and is indicatedin its entirety by the numeral lil.. lt preferably includes a sheath ll, which may consist of a tubular metal member preferably,made` ci Stainless steel or carbon steel, having an l.axial bore I2 and an external cylindrical surface i3,

which is provided with a multiplicity of partially circular parallel grooves le."

The ridgeiportions or cylindrical surfaces i3 between the grooves arel preierably'knurled for nonslippinlg grip with the fingers, and the provision of grooves and ribs also aids in permitting the operator to grip the hand piece without slipping. The partially circular nature of the grooves l permits them to be cleaned more easily, as there are no corners in which dirt'can` accumulate, and aids in maintaining sanitary conditions, VAt itsv left end the sheath Il is provided with linternal threads l5 for engagement with the eX- ternal threads I6 on the front bearingmem'ber il. The Amember il is preferably constructed of stainless steel stock. The iront bearing member Il preferably consists of a tubular metal member, the external surf-aces of which are tapered at I8 and i9 toward the open end, which has a bore 2l). The iront bearing member Il has a tapered counterbore 2l, which serves as a front end bearing for the spindle 22, which has a complementary external frusto-conical surface 231 The front bearing member Il also has an annular shoulder 24 against which the end of the sheath l l abuts ivhen it is threaded home by means ofthe threads At one side the front bearing member is'preferably provided with a threaded bore'25, extending radially, and adapted to receive the screw bolt 2 5 by means of Which other attachments 3 are secured to the front end of the hand piece, in such manner that the attachment housing does not rotate. Such attachments preferably have a spindle that is held in the chuck and a housing that slides on the nose of the hand piece, and have a slot for the screw bolt 25.

The spindle 22 is preferably cylindrical on its outer surface, inside the bearing sleeve |1a, but also preferably has a taper extending from said bearing sleeve toward the end of the spindle, where a relatively sharp tapered surface 23a is provided. The internal surface of the bearing member |1 is complementary in shape.

The spindle comprises an elongated metal member, which is tubular in shape. Over the major portion of its length it has an external cylindrical surface 26. It is provided with an internal cylindrical bore 21, which terminates at the front end in a frusto-conical surface 28 for engaging one end of the collet 29.

The front bearing member |1 is provided with a cylindrical bearing sleeve |1a, having a fric tional t in a complementary recess located at the cylindrical end portion of the front bearing member I1, that is, at the right end, beneath the threads |5.

The spindle 22 is preferably made of steel which is initially plated with a layer of chromium, such as, for example, five thousandths of an inch thick.

This chromium covered steel spindle may be of a hard alloy, and such a combination of chroi' mium plated spindle and hard alloy bearing is adapted to give long use with a minimum amount of wear or vibration.

The collet '29 is adapted to grip the stem of a burr or the shank of a sanding wheel, or any other tool; and it consists of a Vsubstantially tubular metal member having the external cylindrical surfaces 30, 3 32.

The collet 29 has a cylindrical through bore 33, which is approximately the same size as the shank which it is intended to receive, having a close sliding fit with the shank. Each end portion of the collet is provided with a plurality,

preferably three, axially extending slots 34, '35,

the slots being equally spaced in an angular sense and separating the end portions of the collet into three separate legs.

VThe external body of the collet is preferably grooved or relieved at 36 and 31 adjacent the end portions so as to increase the flexibility of the legs, which are formed by the slots 34, 35 adjacent the base of the slots. At each end of the collet there is a tapered or frusto-conical portion 38, 39, which, when engaged by a complementary frusto-conical surface, may tend to cause the end portions of the collet to contract and to grip a shank in the bore 33.

The frusto-conical surface on the front end of the collet at 38 engages the complementary frusto-conical surface 228 inside the spindle. The frusto-conical surface 39 at the other end of the collet, that is, the right end (Fig. 2), engages a complementary inner frusto-conical surface 40 on a plunger 4| The plunger 4| merely consists of a cylindrical metal -member having a sliding fit in the bore 21 of 'the spindle 22. The right end 42 of the plunger may have a plane surface, While the opposite end preferably has a bore 423, and the an- 4 nular end surface terminates in the frusto-conical surface 40, previously mentioned.

The camming action of the frusto-conical surface 39 on the right end of the collet tends, in the devices of the prior art, to cause the plunger 4| to have its left end become expanded at the surface 49.

This causes the devices of the prior art to become larger at the left end of the plunger 4I so that the enlarged cylindrical or deformed surface at the left end of plunger 4| tends to stick in the bore 21. Thus the devices of the prior art were subject to the disadvantage that after a period of years the collet would not let go readily because the plunger 4| `would stick and -Would not slide readily when the tightening rod 44 was released.

Therefore, the plunger 4| is preferably provided with a reduced cylindrical portion 4|a at its left end (Fig. 2), this reduction being exaggerated in the drawings, but consisting of a few thousandths in the actual device.

Such a reduction in size at 4|a insures the plunger 4| against sticking, which might occur due to the slightest enlargement of this end of the plunger 4| under the outward camming action of the frusto-conical surface 39.

The natural tendency of the collet is for its end portions to spring outwardly into cylindrical form; but, when forced toward the left in Fig. 2 by the plunger 4|, the end portions of the collet are cammed inwardly toward each other, diminishing the size of the slots 34, 3'5, while the collet grips a shank. Y

The spindle bore 21 also houses the tightening rod 44, consisting of an elongated metal rod having a plane end surface 45 for abutting against the end 42 of the plunger 4|. Adjacent the end 45 the tightening rod' 44 has Varcylindrieal enlargement 46, which has a sliding t in the spindle bore 21 and centers the tightening rod at this end. At its opposite end in Fig, 3 the tightening rod 44 has a threaded portion 41, the threads of which are complementary to the internal threads 43 in a threaded gland 49, the threaded portion 54 of which engages the internal threads 5| [in the end of the tubular spindle 22.A

A steel knob 52 may be threaded on the end of the tightening rod 44 by means of Va threaded bore 53, and may be secured in place by being soldered to the rod 44 or by a frictional pin 54, which passes through both the knob and the threaded portion of the tightening rod 44. l The cylindrical edge surface 55 of the knob 52V is preferably knurled, and the length of the threaded portion 41 is such as to permit longitudinal adjustment ofthe tightening rod 4 4 by means of its threads 41.

The gland 49 has a radially extending ange provided with a cylindrical knurled surface 56,

but at two diametrically opposite points on the f gland 49 there are parallel flat surfaces 51 for engagement with a small wrench.

The spindle 22 (Fig. 3) may be provided with a cylindrical thrust ring 58 pressed on the spindle, and has an annular surface 59 serving as a thrust bearing. Beyond the thrust surface 59 and toward the right in Fig. 3 the spindle 22 has a reduced cylindrical portion 5D, which serves as a trunnion for engagement in the cylindrical bore El of the rear bearing 62.

This rear bearing member 32 is also preferably constructed of hardened steel or bronze, and is provided with an annular lubricant groove 53 communicating with a radial aperture 64. This aperture communicates with a plurality of radially extending apertures 65, regularly spaced about the periphery of the rear bearing member 62.

These apertures 65 communicate with an annular slot 65a in the inner threaded surface 68 of the Wrist joint frame so that the aperture 65 will be constantly in communication through the slot 65a with the apertures 64, even though the Wrist joint is adjusted longitudinally on the rear bearing member. Lubricant, which enters at 65, nds its way about the spindle 22 in the annular groove 63, from which it spreads longitudinally on the cylindrical trunnion 60 inside the cylindrical bearing 62.

The rear bearing 62 has a substantially cylindrical threaded member 61 adapted to be received in the threaded bore 68 of the wrist joint frame. At the left, beyond the wrist joint frame, the rear bearing 62 has an enlarged cylindrical portion 69, which has a substantial nt in the cylindrical bore l2 Vof the sheath The bore 6| of the rear bearing 82 communicates with an enlarged counterbore 18, beginning at the thrust washer 58, where there is an annular thrust surface engaging the thrust surface 59 on the thrust washer 58.

To the left of the thrust washer 58 the spindle 22 is substantially smaller than the bore 10 in the rear bearing 62 or the bore |2 in the sheath The cylindrical skirt 'I2 on the rear bearing 62 extends into an enlarged counterbore '|3 in the sheath and the length of these two complementary members, that is, this portion of the sheath and the skirt on the bearing serves to lhold the bearing accurately in concentric posi- Vtion with respect to the sheath.

The wrist joint frame is also preferably provided with a radially extending threaded bore 14 (Fig. 3) having a screw bolt 15 which engages a slug 16, driving it into tight engagement with the threads 61 to maintain the adjustment of the wrist joint frame on the bearing 62.

The slug 'I6 has at its end threaded formations complementary to the threads 6l so that the set screw 15 may clamp the slug 'I6 against the threads 6l Without deforming or multilating the threads. its` end as the threads and, as it does not rotate, it does not mutilate the threads.

There is rotating engagement between the slug 'i6 and the screw bolt l5, which preferably has a slot for receiving the screw driver orytool.

It is by means of the adjustment of thewrist joint frame 68 on the threads 61 that bearing wear may be taken up at thefront bearings IT, as

a longitudinal adjustment of the spindle 22 toward this front bearing will cause the tapered surfaces 23 on the spindle 22 and on the bearing I? to come into closer engagement with each other to take up wear. v

The sheath I3 is provided with a radially extending securing flange 11 and a plane end surface '|8 that abuts against the plane end surface 'i9 on the Wrist joint frame 66. The radial flange 'i is preferably circular and adapted to be received in the bore 88 of a unionnut 8|, which has an external cylindrical knurled surface 82. The nut 8| has threads83 in the bore 82 for engaging threads 84 o n the left end of the wrist joint frame 66 (Fig. 3).

An annular surface 85 on the inside of the bore 79 of the union nut 8| engages the radial flange 'Fl and draws the sheath intortight engagement with the wrist joint frame66. 'The union nut 8| has a bore 88 for receiving the The slug 16 is of the same shape at 6 smooth cylindrical body portion 81 of the sheath The spindle 22 has a pulley 88 xedly secured to the right end of the spindle by meansof gland 88, the annular surface 89 of which engages the end of the hub 90 of the pulley 88. The pulley 88 has a cylindrical bore 9| having a sliding t on the right end of spindle 22 (Fig. 3).

The spindle 22 preferably has a partially cylindrical groove 92 extending in an axial direction adapted to receive the pin 93, which is driven into a bore 84 in the hub 90 of the' pulley 88 in such manner that the pin abuts against the end 95 of the bore 95 and projects radially into the bore 98 of the pulley 88 so that it may be received in the groove 93.

The bore 94 is actually in the shape of a groove of cylindrical shape embodying more than half of a cylindrical recess so as to retain the pin 93 in the hub when the pulley 88' is removed. Furthermore, the pin -is driven tightly vinto the hub and substantially riveted and expanded therein. Thus the pulley 88 is prevented from rotating with respect to the lspindle 22, land it is held 0n the Spindle 22 by the gland 49.4

The gear bearing 62 preferably has a tubular extension which is externally threaded at 96; extending inside the bore el'. Bore 91 prevents any lubricant which might iind its way out of the bearing 62 from splashing, and leakage is further reduced by the fact'that the lubricant must pass along the threaded surface 95 toy get on the outsideof lthe bearing'SZ. y

The pulley 88 preferably has a pair of pulley flanges 89, ||l8,`whichl flare, outwardly away from each other and haveV cylindrical outer surfaces lill. The adjacent inner vsurfaces |82, |83 form a V-shapedgroove, which bells outward at the edge of the pulley so as to insure the engagement with thek belt and a tight driving engagement 'by the belt Wedging into the groove |84.

The pulley 88 is preferably provided with a second groove |080, of smaller diameter. This grodve @84a is formed by lthickening the base of the pulley flange |88 and forming itwith a curved t surface |D2`a' which' is opposed te the 'similar curved surface |8311 on the other 'flange lla;

The curved surfaces |A82a and lll'forna V-shaped groove which is annular and whichis adapted'to effec-t fa driving engagement with the same beltthat is used in the groove |84. The difference' inlength of belt required is so small K that it is taken up by the elasticity of the belt.

AThus Vthe present hand piece is provided with a double pulley so thatit maybe driven at the groove |84 'for normal operation and driven at the groove llla to effect higher speeds. Such higher speeds are required for diamond cutting instruments, which should be operated at a higher speed, and which cut more quickly and coolly when so operated. Y

This faster operation reduces'the time 'that is required for drilling or cutting and' reducesthe heat produced in the mouth of the patient, and tends to alleviate the discomfort or pain of the patient during such operations.

The wrist joint frame has a supporting arm-|85,

. which extends radially outward from the body In order to retain the trunnion |08 in the bearing |01 and to limit its motion, the trunnion |08 is provided with a radial stop ||0 rotating .with trunnion |08 over substantially 270 degrees and adapted to engage the reduced cylindrical end of a screw bolt ||2, which is threaded into a threaded bore I |3 located in the part |05.

Thus the wrist joint swivel arm |09 may turn untilfthe end of the screw bolt ||2 engages either end of the stop ||0. Axial movement of the trunnion |08 in the bearing |06 is prevented by the stopI I and shoulder I |0a.

The wrist joint swivel arm has a attened end :portion I |4 which is pivotally mounted in a wristA jointfswi'vel frame ||5 by means of a screw bolt ||6. The wrist joint swivel frame comprises a at 'metal member of substantially triangular form, which is provided with a slot which is rectangular in shape and is bounded by a pair of nat parallel flanges ||8 and ||9.

The slot I |7 extends over the full length of the base of ythe triangle and substantially half way up both of the other sides of the triangle, and this slot is adapted to receive the attened end portions H4, 2| of the front wrist joint swivel arm |09 and the rear wrist joint swivel arm |22;

The latter is pivoted on the wrist joint swivel frame by means of the screw bolt |23. Each of the screw bolts ||6 and |23 have their heads embedded in counterbores in the upper flange ||9 (Fig. 1) and have cylindrical portions adapted to serve as trunnions or pintles located in the slot ||1 and threaded portions threaded into threaded bores in the lower flange I|8, as indicated in dotted lines in Fig; 4.

The intermediate pin |24 is riveted in both of the anges I I8, ||9 and passed through the slot midway between the two screw bolts I |6, |23 and serves as a stop for engaging the flat shoulder |25 on each of the pivot anges ||l|,|2| of the Wrist joint swivel arms. The remainder ofthe edge of the pivot flange is substantially circular, as-indicated at |26,so as to clear the pin |24. Thus the wrist joint swivel arms can move to a position where they are almost in line with each other or to a position in which they extend at an acute angle, as shown in Fig. l, permitting the maximum freedom of l-movement of the hand piece itself in the hands of the operator.

The rear wrist joint swivel arm |22 is provided with any axial bore |21, which extends rearwardly to a point past the radial aperture |28, into which the inwardly turned end of a leaf spring'l29 extends.

The leafspring Vis preferably secured in a groove by having a screw bolt |3| pass through the end of the leaf spring, the bolt being threaded into the arm |22. At its end the tubular arm |22 has an axiallyextending, partially annular portion |32, which engages in a slot -complementary to it on the arm, to which it is attached, this arm having a shank that passes into the bore I2|, and having a hole for receiving the end of the spring |29.

The wrist joint swivel frame ||5 is shown in section kin Fig. 4, and this frame also serves to support a pair of pulleys |33, |34, by means of a wrist joint pulley stud |35. The body of the ;wrist joint pulley 4frame I|5 has a lthrough bore |36, into which the stud is forced, the studY being provided with axially extending knurled formations by means of which it is secured: against rotation with a pressed t. At each end the pulley stud has a reduced cylindrical portion |31, which serves to receive a thrust washer |38 that spaces the pulley from the frame II5, and is engaged by the pulley shaft.

rPhe vpulley stud |35 has each end provided with a reduced threaded portion |39, which is adapted to be received in the threaded bore |40 of the pulley shaft |4I.

The pulley shaft comprises a substantially cylindrical metal member, which has the threaded bore |40, and a smaller counterbore |42 for lubrication, the counterbore |42 being spun over at its end |43 to retain a steel ball |44, which is urged into engagement with the spun-over portion |43 by a compression spring |45, the other end of the spring engaging the reduced threaded end |39 of the pulley stud.

YThe pulley shaft also has a radially extending aperture I 46 whereby lubricant which is forced in past the ball |44 may gain access to the external cylindrical bearing surface I4? of the shaft I4I. The shaft |4| also supports a pulley guard |48 in the form of a substantially circular radially extending flange carried by the pulley shaft MI, which extends beyond the edge of the pulley |34 and has an inwardly extending cylindrical ange |49 overhangingv the outer iiange of the pulley- The guard |48 protects the hands of the operator from the pulleys, but it does not interfere with the pulley belt, andthe guard also prevents the throwing of oil, which might be carried by the pulley to its outermost edge by centrifugal force.

rIVhe pulley guard preferably has an annular thrust surface |50 located to engage the outer end of each pulley so that endwise motion of the pulley on the pulley shaftY is" prevented, and the pulley has a running iit between the washer |33 and the thrust surface |50.

The two pulleys may be identical in construction, and each consists of a circular metal member provided with a centrally located bearing bore |5| for receiving the pulley shaft on which the pulley has a freely .rotating t. At its periphery the pulley is provided with a partially circular groove |52, which is bordered by two radially extending pulley Vflanges |53, |54.

vThe kbelt passes over one of the pulleys |33 to the drive pulley 33,-and thence back over the other vpulley |34 to the usual motor driving mechianism. Y

It will thus -be observed that I have invented an improved dental hand piece which is provided with a double driving pulley so that it is equally adaptable tov drive at normal speeds and at the higher speedsV which are required for diamond cutting instruments.

The present hand piece is so Yconstructed that its collet: will always release the stem of the tool and it will not, after a period of time, tend .to stick and fail to release,Y as in the devices of vproper lubrication of the spindle at all times.

The wrist joint frame arm is provided with animproved built-in form of stop which may be more. cheaply manufactured, and which has no projecting parts that might catch on the clothing of the operator. The wrist joint pulleys are guarded and protected on both sides, and are provided with adequate means for assuring their lubrication at all times and for preventing the pulleys from throwing off lubricant on the operator or the patient.

The present hand piece may be taken apart very easily for inspection of its parts or for cleaning, and it is also adapted to be maintained in a sanitary condition with a minimum amount of labor.

While I have illustrated a preferred embodiment of my invention, many modifications may be made Without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is:

1. In an improved wrist joint, the combination of a solid metal body of rounded triangular shape provided with a through bore at one side and having a pair of parallel flanges separated by a slot at each of its ends, a metal shaft having a longitudinally knurled cylindrical surface having a pressed iit in said through bore, wrist joint members pivoted between said flanges in said slots, said shaft having a reduced threaded portion at each of its ends, a combined guard and trunnion member for each end of said shaft, Said members each having a cylindrical portion threaded on 'the shaft to form a trunnion, and having an integral radially extending guard body acting as a thrust bearing, each of said trunnions rotatably supporting a circular pulley having a partially circular groove in the periphery of each pulley bordered by radially projecting edge flanges, said guard having a substantially cylindrical guard flange extending axially over the adjacent edge flange of the pulley in position to prevent the pulley belt from getting in between the pulley and the guard.

2. In an improved wrist joint, the combination of a solid metal body of rounded triangular shape provided with a through bore at one side and having a pair of parallel anges separated by a slot at each of its ends, a metal shaft having a longitudinally knurled cylindrical surface having a pressed t in said through bore, wrist joint members pivoted between said flanges in said slots, said shaft having a reduced threaded portion at each of its ends, a combined guard and trunnion member for each end of said shaft, said members each having a cylindrical portion threaded on the shaft to form a trunnion, and having an integral radially extending guard body acting as a thrust bearing, each of said trunnions rotatably supporting a circular pulley having a partially circular groove in the periphery of each pulley bordered by radially projecting edge flanges, said guard having a substantially cylindrical guard flange extending axially over the adjacent edge flange of the pulley in position to prevent the pulley belt from getting in between the pulley and the guard, the said guard member having a central bore communicating with its threaded bore and forming a lubricant reservoir, said central bore terminating at its outer end at the face of the guard in an inwardly turned retaining flange, a ball valve in said central bore engaging said retaining iiange and a spring engaging the end of the threaded shaft and engaging said ball to re tain lubricant, the said trunnion having a through radial bore leading from said central bore to its bearing surface.

MARTIN STAUNT.

REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS Number Name Date 193,300 Tripp July 17, 1877 440,128 Bonwill Nov. 1l, 1890 464,568 Johnsoln Dec. 8, 1891 1,336,413 Bates Apr. 13, 1920` 1,733,762 Tisdall Oct. 29, 1929 1,753,773 Champion Apr. 8, 1930 1,835,961 Pieper Dec. 8, 1931 1,839,289 Angell Jan. 5, 1932 1,900,874 Wallgren Mar. 7, 1933 2,249,058 Staunt July 15, 1941 FORETGN PATENTS Number Country Date 355,551 Great Britain Aug. 27, 1931 

